This invention relates to a filling or packing body of acid-resistant synthetic plastics material, a plurality of which, heaped up in an irregular manner, will constitute, per cubic meter (m.sup.3) of bulk volume, a total surface, of all bodies therein, of more than 250 m.sup.2.
Filling bodies of many different shapes are known which are used for improving the exchange of material between streams of gas and liquids. Widely used are, for instance, ring-shaped elements known as Raschig rings, Pall rings, Berl saddles, flat triangular elements and other types.
Among the techniques of chemical processing, there are many involving the use of filling bodies having a large surface. Where total surfaces of filling bodies of more than 250 m.sup.2 per m.sup.3 of gas-liquid contact space are required, the number of such bodies is generally above 50,000 per m.sup.3, resulting in correspondingly high production costs. When producing filling bodies from metal, it is possible to use very thin metal sheets, affording a free volume of more than 94% calculated on the total volume occupied by such body. However, filling bodies made from acid-resistant metals are very expensive, especially where large surfaces and correspondingly large numbers of bodies per unit of volume are required.
Gas purification methods are known which require the use of filling bodies in layers having a total height of 5 meters, and in which the filling bodies must be of ceramic or of synthetic plastics material. Such methods involve, for instance, the purification of nitrogen oxides with sulfuric acid, and are described in
Ullmanns Enzyklopadie der technischen Chemie, 4th revised and enlarged edition, published by Verlag Chemie, Weinheim, Germany, Vol. 21 (1982), page 148; and PA0 U.S. Pat. Nos. 4,148,868 (1979) and 4,242,321 (1980), both assigned to Ciba-Geigy Corporation, Ardsley, N.Y.
The lower portion of the heaped-up layer of filling bodies is subject to a relatively high pressure resulting from the weight of the superimposed filling bodies and in addition, from the weight of the sprayed-on or sprinkled-on acid. Reasonably inexpensive acid-resistant synthetic resin materials, such as polyethylene, are already relatively soft when they are to be used for the manufacture of thin-walled filling bodies.
In the denitration zone of a nitrogen oxides/sulfuric acid system, temperatures of up to 120.degree. C. may prevail. While filling bodies of fluoro hydrocarbons such as polyvinylidenefluoride (PVDF) are chemically resistant, they can only be applied at reasonable cost when it is possible to produce them from extremely thin-walled material.